1. Field of the Invention
This invention relates to an electric receptacle for a wall outlet box.
2. Description of the Prior Art
The prior art of ground fault interrupter receptacles is limited at present, because they are in the development stage. A difficulty with such receptacles heretofore has been that receptacles with ground fault protection have been too large to mount in a conventional wall outlet box without the use of a fixture or extension block. One reason for the large size is that the receptacle with ground fault monitors contains electronic components, such as relays and solenoids. But a need exists for a receptacle with ground fault protection and having a compact size to enable insertion into a standard wall outlet box and which provides satisfactory electrical performance exists. One type of electric receptacle assembly with ground fault protection is that shown in U.S. Pat. No. 3,813,579.
Most receptacles with ground fault protection have involved various problems. First, the standard wall outlet box has been used with receptacles without ground fault protection. A receptacle having ground fault protection means involves additional parts that must be assembled in the same space as the original receptacle. There is also a problem of nuisance tripping incurred by the magnetic flux developed by the power source conductors which necessarily pass through the sensor coil of the ground fault detector. More particularly, the segments of the conductor are proximate to the coil due to the requirements of compactness of the assembly. As a result the magnetic flux in each conductor causes the coil to respond to current imbalances not incurred by real ground fault causes. In addition, other segments of the conductors on the opposite side of the sensor coil are connected to a contact carrier switch arm which must be free to move in response to ground fault causes and uninhibited by any mechanical force due to the wire.
Associated with the foregoing has been a need for a trip-free construction by which the receptacle cannot be reset so long as a ground fault continues to exist. It is desirable to provide the trip-free feature even though a reset button is held manually in place.